Traffic engineering concerns an optimization of the overall performance of a network, and mainly aims to provide a highly effective and reliable network service, to optimize the use of network resource, and to optimize network traffic. In particular, there are two aspects: one is traffic-oriented, i.e. to concern how to improve the quality of service of the network; the other is resource-oriented, i.e. to concern how to optimize the use of network resource, mainly the effective utilization of bandwidth resource. With the increase of deployment and development of General Multi protocol Label Switching (GMPLS), inter-domain traffic engineering will span different operators and covers the GMPLS network.
Constrained path computation, e.g. Constrained Shortest Path First (CSPF) computation, is an important component of Multi protocol Label Switching (MPLS) and GMPLS traffic engineering. Path computation among multiple autonomous systems is complex, because computation elements within different autonomous systems should cooperate with each other for accomplishing the computation. A Path Computation Element (PCE) model-based path computing method may be applied to the inter-domain traffic engineering. The computing method does not affect the use of a computed path (the use of a computed path means, for example, establishment, maintenance and disconnection of a Label Switched Path (LSP)), but for computation of such an LSP.
In the PCE model-based path computing method, if a Path Computation Client (PCC) such as an ingress Label Switching Router (LSR) desires to establish an LSP, it first sends a request to a PCE, the request including basic information such as path destination and various constraint conditions. The PCE receives the request, and computes a path meeting the constraint conditions of the request in accordance with information such as Traffic Engineering Database (TED) and topology synchronized with the network, and returns the path to the PCC through a response message. The path is taken as an Explicit Route Object (ERO) parameter for establishing the LSP by the PCC. The computed path may include explicit nodes (e.g. a router) and loose nodes (e.g. a network segment, an area, or an autonomous system).
In the PCE model-based path computing method, computation made by each PCE usually covers an autonomous system. Particularly, the autonomous system is a range in which Traffic Engineering Database (TED) messages are distributed through an Internet Gateway Protocol (IGP).
In the PCE model, two basic protocols are needed: a PCE discovery protocol, responsible for PCC's discovering the existence of PCEs and computation capability thereof, and selecting a proper PCE to which a computation request is sent for computation in accordance with the information obtained from the protocol if the PCC has the computation request, and a PCE communication protocol, mainly responsible for transporting computation requests and response messages between PCC and PCE. The computation request from the PCC contains various constraint conditions. If a PCE receives a path computation request which is specified to be processed locally, the PCE will perform a path computation accordingly.
At present, corresponding overall requirements are proposed for the PCE communication protocol. However, no corresponding solution is proposed for particular issues involved in the requirements, and no solution is proposed for possibly confronted issues as mentioned in the requirements.